The present invention relates to a molecular sieve arrangement.
Natural and synthetic zeolitic molecular sieves are suitable for the separation of mixtures of inorganic and organic substances and for the removal of undesired impurities from gases and liquids. One current field of application of molecular sieves is the drying of gases and liquids, for example, acetone, butane, toluene, etc.
Molecular sieves are also used for the removal of carbon monoxide, hydrocarbons, nitrogen, methane and so on from air. They are further used in ion exchangers.
Molecular sieves within the scope of the invention can consist of natural or synthetic zeolites. Synthetic zeolites frequently have the same crystal structure as natural zeolites. Natural zeolites may, for example, be aluminum silicates having the general formula ##EQU1## where Me denotes the alkali metal ion (n=1), mostly Na or K, or the alkaline earth metal (n=2) which is normally Ca and more seldom Ba, Sr and Mg. Most of the ad/absorbents are included in this category.
The mechanics of separating molecules from liquid or gaseous media by means of molecular sieves involves adsorption with the molecular sieve functioning as an adsorbent and influencing the adsorption through the magnitude and energy characteristics of its surface. The adsorption of ions, molecules or molecular agglomerates and the like--the adsorbates--is limited by the energy characteristics of the boundary layer between the two phases. The adsorbed molecules continuously coat the inner surface of the adsorbent and cover the same. Accordingly, saturation occurs after a certain amount of time and prevents further adsorption.
The known separating processes use only molecular sieves having a pore size of 3 Angstroms or greater than 3 Angstroms in order to permit the entry of molecules to be filtered out of gases or liquids, that is, in order to make the vast inner surface of the molecular sieve usable.
The zeolites of the natural analcite group, whose pores have a size of the order of 2.6 Angstroms, have not been used as molecular sieves because the molecules to be adsorbed or absorbed cannot, due to their size, penetrate into the primary pores of the analcite zeolite. The smallest molecule, which is the water molecule, measures only about 2.9 Angstroms (see "MOLEKULARSIEBE" by Otto Grubner, Pavel Jiru and Milos Ralek, VEB Deutscher Verlag der Wissenschaften, Berlin 1968, page 27).
The disadvantageous property of the known molecular sieves is that the inner surfaces thereof are directly loaded and, depending upon molecular sieve type, no further molecules can be taken up once the adsorbate proportion has increased to about 25%.
Loading of the inner surfaces of the conventional molecular sieves already occurs upon contact with the surrounding air and the water molecules contained therein. Accordingly, the capacity is reduced in two respects.